Slope instability (landslides)
The mountainous hinterland of the Gold Coast has steep slopes, is subject to intense rainfall and has been extensively developed. Natural landslides have been recognised over large areas of the hinterland. Council has undertaken a slope analysis to assess possible areas and levels of risk. The results of this study are available from Council as a search upon payment of a fee.What is a landslide?
A landslide (or landslip) is a downslope movement of a soil or rock mass as a result of shear failure at the boundaries of the mass. The displaced material mass can be large or small, and may move an extensive distance at considerable velocity. Soil creep, which is slow and occurs without a well defined failure surface, is not included as a landslide.
Landslide movement occurs in three main forms:
- by sliding along a failure surface
- by failing down a steep slope
- by flowing as a suspended mass, usually in water, for example mudslide or debris flow
What causes landsliding?
The stability of sloping ground is controlled by three main factors:
- the angle of the ground surface
- the strength of the materials below the ground surface
- the level of water within the slope
The effects of development on sloping sites can significantly change slope stability.
How can landslide potential be evaluated?
The potential for landslide requires consideration of the factors that contribute to landsliding. In many cases most site conditions can be obtained during a walk-over survey by an experienced and suitably qualified geotechnical professional. It may be necessary to supplement the site observations by subsurface investigations such as boreholes or test pits.
Further information
For further information on slope instability, or a copy of our Guidelines for Control of Slope Instability within the City of Gold Coast, contact Ecological & Hydraulic Assessment:
- Phone: (07) 5582 8866
- Fax: (07) 5582 8248
- Email:
gcccmail@goldcoast.qld.gov.au
